Abstract:
A survey was carried out in the Kwaebibirem District of the Eastern Region of Ghana to identify insect pests and natural enemies of upland rice both in the field and storage. The study lasted from September 1999 to October 2000. Field insects were sampled from five communities in the district i.e. Agricultural Research Station (ARS)-Okumaning, Subi, Abodom, Abaam and Prankese. Two line transects twenty five meters apart were fixed through each rice field. On the first line transect, insects were collected by walking and sweeping with net. On the second line transect, ten hills were marked. The tillers of marked hills were examined visually. Insects found on the tillers at different crop growth stages were determined, identified and counted on each sampling period. In storage, tied bundles of paddy of 100 panicles each were stacked into heaps and stored in a wooden ban at an initial moisture content of 15%. Sticky and crevice traps were used to monitor insect activity. Two bundles each of tied paddy were selected, from the top layer, middle layer and bottom layer, placed in plastic bags and frozen for 12 hours to kill insects. These bundles of paddy were untied and mummified insect bodies were identified and counted. Students t test (P = 0.05) was used to test for significance. Twelve insect pest species from nine families were identified from the field studies. Of these Diopsis thoracica (Diptera: Diopsidae) represent 65%, Conocephalus longipennis, Taphronota sp., Turbida sp., Acrida sp., Catoptropteryx sp., Zonocerus variegates (Orthoptera) 25% and Aspavia sp., Nezara sp., Oebalus sp. (Pentatomidae) 10% of the total number of insect pests sampled.
Spiders (unidentified) formed 75% of the number of natural enemies. Odonata (Palplopluera lucia, Orthetrum stemmate, Enallagma sp., Agriocnemis sp.) formed 10%. Menochilus sexmaculales (Colcoptcra: Coccincllidae) and Harmonia octomaculata (Coleoptera: Coccinellidae) also formed 5%. Temelucha sp. (Hymenoptera: Ichneumonidae), Plistospiloia guineenis, Chlidonoptera chopardi (Orthoptera) 5% and Ants (unidentified) 5%. A total of five species of store-product insect pests were identified. The two most abundant primary insect pests were Sitotroga cereallela (Oliver) and Siiophilus sp. Secondary insect pests collected in increasing order of abundance were Gnatocerus maxillosus (Fab), Tribolium castaneum (Herbst) Rhyzopertha
ominica (Fab) and Carpophilus dimidiatus (F). Seven natural enemies were recorded during the storage of grains. These included cereal psocids, parasitic wasps, ants, fire brats, pseudoscopions and spiders. The study indicated that the overall pest situation in the study area was not alarming, a situation which could be attributed to growing of paddy under shifting cultivation by farmers and the presence of natural enemies.
